Datasheet

03 | Keysight | U1240 Series Handheld Digital Multimeters - Data Sheet
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Test Confidently and Efficiently
Harmonics ratio
In real life, harmonics are present in AC power due to the fact that many electronic
devices are powered by switched mode current pulses which travel back into the power
source. If these unwanted harmonics become too large, the undesirable side effects
include: overheating that shortens the lifespan of motors, generators and transformers,
premature tripping of circuit breakers, and blown fuses. One of the fastest ways to detect
and gauge the percentage of distortion due to harmonics is by measuring the harmonic
ratio of the incoming AC voltage. You can perform this very easily on the U1242B/C
handheld DMM, with just a button press. The percentage helps you to decide if further
analysis of the power source is required with an oscilloscope or a spectrum analyzer.
Low impedance mode (Z
low
)
Stray voltages are usually encountered in non-energized electrical wiring adjacent to
powered wires due to capacitive or inductive coupling between these wires. The low
impedance mode helps to reduce false readings by dissipating these stray voltages thus
improving safety and measurement efficiency during voltage measurement.
Vsense for non-contact voltage detection
Vsense is a unique method of non-contact voltage detection that safeguards users
from exposure to hot or live wires while making measurements in dangerous working
environments. Upon detection of high AC voltage, it produces a unique combination of
beeping audio and blinking LED light to alert users.
Dual and differential temperature
In the installation, maintenance and troubleshooting of heating, ventilation and
air-conditioning (HVAC) systems, temperature measurements are essential. As an
example, to ensure boiler temperature adheres to safety requirements, you would need
to measure both boiler and air temperature simultaneously to achieve accurate real-time
readings. With a faulty air conditioning system, viewing the temperature difference
between warm return air and cool air supply helps to reveal the cooling behavior of the
evaporator with respect to time. Now with the convenience of the U1242B/C DMM, you
need only one instrument to efficiently get dual and differential measurements.
Solar heating system Air conditioning system
Pump
Controller
Solar collector
To taps
Warm
air out
Warm return air in
Tank
Cold water feed Expansion valve
Evaporator blower
Metering
device
Evaporator
CondenserCompressor
Boiler
Cool supply
air out
Condenser fan
Ambient (outside) air in
Figure 1. Dual and differential temperature for efficient testing of HVAC systems